I am using this code to add an onkeypress attribute to a textbox control on a form:

        loControlTextboxUsername.Attributes.Add("onkeypress", "return FormLoginFromInput(event)")

However, on Mozilla Firefox, the attribute does not get added. So, this means .NET is smart enough to detect the browser and ignore that line. Or, is there something I am missing?

And, if that is the case, then, what kind of approach should I use to make sure this will be added on all browsers or how to have it compliant with all browsers?